1. Centre for Auditory Research, UCL Ear Institute, London, WC1X 8EE, UK
2. Institute of Structural and Molecular Biology, Birkbeck College, London WC1E 7HX, UK
3. Neuroscience, Physiology & Pharmacology, UCL, London WC1E 6BT, UK
4. Centre for Ultrastructural Imaging, King's College London, London WC2R 2LS, UK
5. National Institute for Biological Standards and Control, Potters Bar, EN6 3QG, UK